The new suspected test comes after the United States imposed new sanctions this week, prompting Pyongyang to vow never to give up its "right to self defence".

"North Korea fires unidentified projectile eastward," Seoul's Joint Chiefs of Staff said Friday without giving further details.

Japan's coast guard said it had detected "the launch from North Korea of what appears to be a ballistic missile or missiles at 14h55". (0555 GMT)

A coast guard spokesman told AFP it was still analysing where it fell and whether it was one object or multiple.

Despite biting international sanctions over its nuclear weapons programme, Pyongyang tested what it said were hypersonic missiles on January 5 and January 11.

After the second test, which was personally supervised by leader Kim Jong Un, the United States imposed additional sanctions on five people linked to North Korea's ballistic weapons programme.

The move prompted accusations from a foreign ministry spokesman in Pyongyang that the United States was "intentionally escalating" the situation.

If "the US adopts such a confrontational stance, the DPRK will be forced to take stronger and certain reaction to it," the spokesman said in comments carried by state news agency KCNA earlier on Friday.

It is North Korea's "legitimate right" to develop new weapons as part of its drive for "modernizing its national defence capability," the spokesman said.

- 'Worrisome' situation -

Yang Moo-jin, a professor at the University of North Korean Studies, told AFP that the timing of the latest suspected test was concerning.

"This situation is worrisome. North Korea launched this test right after releasing a statement saying they are not going to give up their 'right to self-defence,'" Yang said.

"With the test, they showed that they really meant what they said in the statement. The message is very clear. North Korea is not going to give up anything when it comes to its weaponry despite the newly imposed sanctions."

On Thursday, US Secretary of State Antony Blinken called on North Korea to sit down for talks with the United States, which he said harboured no "hostile intent" toward Kim Jong Un's regime.

The continued tests are "profoundly destabilising, it's dangerous, and it contravenes a whole host of UN Security Council resolutions," Blinken said in a televised interview.

Pyongyang has refused to respond to US appeals for talks.

At a key meeting of North Korea's ruling party last month, Kim vowed to continue building up the country's defence capabilities, without mentioning the United States.

Dialogue between Washington and Pyongyang remains stalled, and impoverished North Korea is also under a rigid self-imposed coronavirus blockade that has hammered its economy.